thank you for your reply and the potential fix.
This fix would only reset my custom action I guess. If my graph would use built-in actions or actions which require a return value, the graph would still be broken, or not?
Maybe not, because I did some further testing: It seems that the Finish Action is not reset properly because it stops the graph during execution of that action. If I manually reset all nodes (as done in Graph.Stop) before I start the graph again everything looks fine.
So, the EndAction(null) call might be the fix because it enables my Finish action to be reset.
Can you confirm this guess?